Shoe sole and method

ABSTRACT

A shoe outsole and method of manufacture wherein the outsole is formed using recycled rubber granules generated during the shoe manufacturing process, the recycled rubber granules being used as a filler material and being mixed with various thermoplastic materials or vulcanized rubber to form the shoe outsole. The recycled rubber granules are mixed with the thermoplastic material or vulcanized rubber to form a filled elastomer which includes at least 50% by weight of a virgin thermoplastic material and no more than about 30% by weight of the recycled rubber granules.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to U.S. Provisional Patent Applications Ser. No. 61/169,763, filed Apr. 16, 2009, entitled SHOE SOLE AND METHOD, which application is hereby incorporated by reference to the extent permitted by law.

BACKGROUND OF THE INVENTION

The present invention relates generally to the construction of a shoe and the manufacture thereof and, more particularly, to the construction of a shoe having an outsole comprised of a granular rubber scrap material in combination with vulcanized rubber or various thermoplastic materials, the rubber scrap material being generated during the manufacture of shoes.

The shoe industry is faced with many issues. One of these issues is cost control while maintaining product quality. One cost issue is directed to the disposal of scrap materials from the shoe making process, particularly rubber scrap. Another issue is the manufacture of quality shoe outsoles while controlling the cost thereof. As the price of hydrocarbons increases, materials made from crude oil increases, including the cost of producing many types of elastomers used in outsoles.

During the manufacture of shoes, various materials such as synthetic and natural rubber, thermoplastics and thermosetting or cured plastics and leather materials are cut into a desired shape to fit a particular pattern or design. As a result of the cutting process, portions of these materials are discarded as scrap. Currently, the trimmings are a stream of scrap material that must be disposed of. Today, the scrap material is disposed of in landfills since there is no current use for it, particularly the grindings. The disposal of waste in landfills can be expensive.

The inventor of the present invention has previously developed a process for the manufacture of outsoles with fillers made from recycled granular scrap material as disclosed in U.S. patent application Ser. No. 12/420,031, filed Apr. 7, 2009. This earlier process utilizes recycled leather or jute for use as a filler in the manufacture of shoe outsoles. During the course of designing specific formulations for fillers using the recycled materials of the prior process, it was found that the specific formulation of blending certain virgin thermoplastic elastomers or vulcanized rubber with recycled rubber material produced outsoles having enhanced properties such as improved integrity when compared to outsoles manufactured using conventional processes. In view of this finding, various compositions comprising a mixture of virgin thermoplastics, vulcanized rubber, and recycled rubbers were developed, tried and tested.

In the manufacturer of shoes, it is common to use rubber to form parts of the shoes including outsoles. As a result, scrap rubber material is generated during the manufacturing process. It would be desirable to utilize granular rubber scrap materials as fillers for addition to the elastomeric material used in outsoles to control cost while maintaining the functionality and appearance of the outsole.

It would also be desirable to provide a shoe outsole and method of making the shoe outsole that reduces the cost of the outsole by utilizing scrap rubber material generated during the shoe making process as a filler with vulcanized rubber or a variety of thermoplastic elastomers without adversely affecting the quality or appearance of the outsole and, in fact, enhancing the quality and appearance.

It would also be desirable to utilize the scrap rubber material generated during the shoe manufacturing process as a manufacturing material rather than disposing of it as a waste material. As the price of raw materials increases, the ability to use a material that is currently a waste material in place of costly raw materials would be desirable.

It would also be desirable to provide a process for the manufacture of high quality thermoplastic rubber compositions which promotes interfacial adhesion between the virgin thermoplastic component and the recycled rubber component.

An improved method of making an eco-friendly outsole which utilizes available waste material generated during the shoe making process is also desirable.

SUMMARY OF THE INVENTION

The present invention is directed to the use of recycled rubber material generated during the manufacture of shoes. The shoe includes an upper, a midsole and an outsole. The outsole is secured to the upper or midsole such as by cementing and/or stitching and has a bottom surface portion with a heel region and a forefoot region. The recycled rubber materials are ground to an effective particle size and then added to raw outsole material during compounding or secondary mixing.

In one aspect of the present invention, a method of making a shoe outsole using recycled rubber material generated during the shoe making process as fillers is disclosed. The recycled rubber material is added to either vulcanized rubber or a variety of thermoplastic elastomers including thermoplastic rubber (TPR) to form a filled elastomer. The filled elastomer is then formed into an outsole for a shoe. The outsole is then attached to a shoe upper to form a shoe.

In another aspect of the present invention there is provided a process for forming a molded shoe outsole from a granular scrap material comprising a recycled rubber which is used as a filler with a base material such as a vulcanized rubber, or a virgin TPR or a combination of reground TPR and virgin TPR. The percentage by weight of the base material is at least 70%, while the recycled rubber granules are 30% or less. Generally, the granular scrap rubber material and the base material are mixed under sufficient pressure and temperature for a sufficient time to at least partially plasticize some portion of the materials and form a moldable product. The plasticized moldable material may then be molded, for example, by injecting the plasticized material into a mold.

Shoe outsoles made in accordance with the teachings of the present invention can be obtained from blends of recycled rubber with a vulcanized rubber or a variety of thermoplastic materials by varying the ratio of components in the blend, or by changing the components themselves. The thermoplastic material preferably is, but need not be entirely, a virgin thermoplastic material. A variety of thermoplastic materials may be used according to the present invention, provided that they are compatible with the recycled rubber.

In the case of vulcanized rubber, the process for forming the outsole of the present invention may include the steps of mixing the recycled rubber granules with the vulcanized rubber in a Banbury® or suitable mixer to form a uniformly distributed mixture; milling the mixture on a roller mill to add colorants and/or processing materials; and then molding the milled material into an outsole.

In the case of a thermoplastic elastomer, the process for forming the outsole of the present invention may include the steps of mixing the recycled rubber granules with the thermoplastic elastomer in a Banbury or suitable mixer to form a uniformly distributed mixture. The mixture is then extruded into rods and then chopped or cut into pellet form. The thermoplastic raw material thus formed is then injection molded into the form of an outsole.

The resulting outsoles using these recycled rubber granules have improved physical characteristics while significantly reducing manufacturing costs.

Specific advantages and features of the present invention will be apparent from the accompanying drawings and the description of several illustrative embodiments of the present invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of one embodiment of a shoe having an outsole constructed in accordance with the teachings of the present invention.

FIG. 2 is a fragmentary cross-sectional view of the outsole of FIG. 1 taken along line 2-2 of FIG. 1.

It should be understood that the drawings are not necessarily to scale and that the embodiments disclosed herein are sometimes illustrated by fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. It should also be understood that the invention is not necessarily limited to the particular embodiments illustrated herein. Like numbers utilized throughout the various figures designate like or similar parts or structure.

DETAILED DESCRIPTION

As illustrated in FIG. 1, the present invention provides a shoe 2 generally comprising a shoe upper 7, a midsole (not shown) and an outsole 1. The outsole 1 has an outer perimeter, a portion of which is noted as 4, a bottom surface 5 and a top surface 6 (FIG. 2) to which the shoe upper 7 is secured. The outsole 1 is typically made of an elastomer material that can be either a thermosetting or thermoplastic type. Such materials are well known in the art of shoe soles and can include, but are not limited to, elastomers such as polyvinyl chloride and styrene block copolymers (thermoplastics) and cast polyurethane and vulcanized rubber (thermosets). The elastomer is a material of high molecular weight which, in the vulcanized state at room temperature, can generally be stretched repeatedly to at least twice its original length and which, upon release of the stress, will return to approximately its original length. The term elastomer in this application is used loosely to include various macromolecular and microcellular materials, natural or synthetic, which have rubber-like properties and which can be combined with recycled rubber granules as will be hereinafter discussed.

The outsole 1 includes a filler material 8 that is derived from the shoe manufacturing process, namely, recycled rubber granules. The ratio of the granular scrap rubber material to the elastomeric base material may vary over a wide range depending upon the ultimate characteristics desired in the outsole. In one embodiment of the present invention, the filler 8 which is recycled rubber granules, is added to the elastomeric base material in a weight range not to exceed about 30% by total weight of both the base material and filler, that is, the total weight of the recycled rubber granules and base material on a dry weight basis. For example, the percentage by weight of the base material in one formulation might be about 80%, while the recycled rubber granules might be about 20%; in another formulation, the percentage by weight of the base material might be about 75% while the recycled rubber granules might be about 25%. However, in order to obtain integrity of the mixed material, the base material should be comprised of at least 50% by total weight of a virgin thermoplastic elastomer or at least 50% by total weight of vulcanized rubber. This percentage of vulcanized rubber or virgin thermoplastic material ensures that the mixed material will combine and mold correctly. Other materials can be added to the elastomer or elastomer/filler mixture such as, for example, carbon black, colorants or other suitable materials which are known in the art so long as the percentage of recycled rubber granules does not exceed about 30% by total weight of the entire composition and so long as the percentage of vulcanized rubber or virgin thermoplastic material is at least 50% by total weight of the entire composition. In the use of the above-described recycled rubber material as filler 8, the addition of the present filler material reduces the amount of elastomer needed to form an outsole, thus reducing the cost of producing an outsole while maintaining functionality and appearance. The use of the present invention can also eliminate disposing of the scrap rubber material in a landfill.

A suitable thermoplastic elastomer or vulcanized rubber is provided in bulk. It is then mixed preferably in a suitable mixer with the recycled rubber granules. The filler material is added to the elastomer material prior to its being formed into an outsole, preferably in bulk form and mixed with the elastomer.

In one embodiment, the recycled rubber material collected from the shoe manufacturing process is ground and/or pulverized in a conventional grinding and pulverizing apparatus to achieve the desired particle size. Preferably, the recycled rubber is ground to a homogeneous mix having an average particle size less than about 2 mm. The recycled rubber materials are mixed with a thermoplastic elastomer or vulcanized rubber in a Banbury® or suitable mixer for mixing or compounding plastics and interspersing reinforcing fillers. In one embodiment, the mixed materials are passed through a roller mill to add colorants and processing materials, and then they are processed via injection molding, compression molding, transfer molding, or some other similar process. The mixed and milled materials are then molded into an outsole. In injection molding, thermoplastic materials are heated and liquified before entering the mold. The mold is not heated so that the heated liquid cools and sets, or returns to a solid form in the shape of the mold. Sometimes chemical accelerators are used with certain materials, such as polyurethane, and are mixed in the machine head and rapidly injected into the mold because of the speed of the reaction.

In the case of vulcanized rubber, the process for forming the outsole of the present invention includes mixing recycled rubber granules with the vulcanized rubber in a Banbury or suitable mixer to form a uniformly distributed mixture; milling the mixture on a roller mill to add colorants and/or processing materials; and then molding the milled material into an outsole.

In the case of a thermoplastic elastomer, the process for forming the outsole of the present invention may include the steps of mixing the recycled rubber granules with the thermoplastic elastomer in a Banbury or suitable mixer to form a uniformly distributed mixture. Compression molding can also be used. The mixture of elastomer and filler can be extruded into rods or ribbons and then cut into pellet form. The mixture could also be added in bulk to an extruder. The formed pellets can be added to the hopper of the extruder as a feed material. The filled elastomer material can then be heated in the extruder to a flowable temperature and injected, as is well known in the art, into a mold cavity to form the outsole 1. An injection mold is typically cooled or maintained at a temperature below the melting temperature of the thermoplastic elastomer, allowing the outsole to set or solidify in its as-molded form, removed from the mold and then processed into finished shoes by securing the molded outsole 1 to a shoe upper 7 as with cement and/or stitching to form the shoe 2.

In still another embodiment of the present invention, the base material may be comprised of both a thermoplastic material and a reground thermoplastic material such as virgin TPR and reground TPR. In this particular embodiment, the recycled rubber granules will be mixed with the combination of a virgin thermoplastic material and a reground thermoplastic material. Here again, the virgin thermoplastic material must be present in the overall formulation in an amount equal to at least 50% by total weight of the entire composition and the recycled rubber granules must be present in an amount not to exceed about 30% by total weight of the entire composition. This means that the remaining portion of the total composition can be comprised of reground thermoplastic material, or reground TPR, or other materials compatible with the overall composition. For example, one embodiment of the present outsole constructed and manufactured in accordance with the teachings of the present invention may include by total weight about 30% recycled rubber granules generated from the shoe manufacturing process or elsewhere, about 20% reground TPR, and about 50% virgin TPR. In another embodiment, the present outsole may include by total weight about 30% recycled rubber granules, about 20% reground thermoplastic material, and about 50% virgin thermoplastic material. Other combinations are likewise envisioned and anticipated so long as the recycled rubber granules do not exceed about 30% by total weight of the entire composition, and so long as the thermoplastic elastomer includes at least 50% virgin thermoplastic material by total weight of the entire composition.

Thus, there has been shown and described several embodiments of a novel invention. As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. The terms “having” and “including” and similar terms as used in the foregoing specification are used in the sense of “optional” or “may include” and not as “required”. Many changes, modifications, variations and other uses and applications of the present invention will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow. 

1. A method of making a shoe outsole comprising the steps of: providing recycled rubber granules; mixing the recycled rubber granules with a thermoplastic elastomer to form a filled elastomer; and forming the filled elastomer into an outsole.
 2. The method of claim 1 wherein the thermoplastic elastomer is a virgin thermoplastic material, and wherein the filled elastomer includes at least 50% by weight of the virgin thermoplastic material.
 3. The method of claim 1 wherein the filled elastomer includes no more than about 30% by weight of the recycled rubber granules.
 4. The method of claim 1 wherein the thermoplastic elastomer includes virgin thermoplastic rubber, and wherein the filled elastomer includes at least 50% by weight of the virgin thermoplastic rubber.
 5. The method of claim 1 wherein the thermoplastic elastomer includes a thermoplastic material and a reground thermoplastic material, and wherein said filled elastomer includes at least 50% by weight of the virgin thermoplastic material.
 6. The method of claim 5 wherein said filled elastomer includes about 30% by weight of said recycled rubber granules, about 50% by weight of said virgin thermoplastic material, and about 20% by weight of said reground thermoplastic material.
 7. The method of claim 6 wherein said reground thermoplastic material includes reground thermoplastic rubber.
 8. The method of claim 6 wherein said virgin thermoplastic material includes virgin thermoplastic rubber.
 9. A method of making a shoe outsole comprising the steps of: providing recycled rubber granules; mixing said recycled rubber granules with vulcanized rubber in predetermined quantities to form a filled elastomer; and forming the filled elastomer into an outsole.
 10. The method of claim 9 wherein said filled elastomer includes at least 50% by weight of said vulcanized rubber.
 11. The method of claim 9 wherein said filled elastomer includes no more than 30% by weight of said recycled rubber granules.
 12. A method of making a shoe outsole comprising the steps of: providing recycled rubber granules; mixing said recycled rubber granules with virgin thermoplastic rubber and reground thermoplastic rubber in predetermined quantities to form a filled elastomer comprising at least 50% by weight of said virgin thermoplastic rubber; and forming the filled elastomer into an outsole.
 13. The method of claim 12 wherein said filled elastomer includes no more than 30% by weight of said recycled rubber granules.
 14. A molded shoe outsole comprising: a thermoplastic elastomer; and recycled rubber granules mixed with said thermoplastic elastomer to form a filled elastomer, said filled elastomer including no more than about 30% by weight of said recycled rubber granules.
 15. The molded shoe outsole of claim 14 wherein said thermoplastic elastomer includes a virgin thermoplastic material, said filled elastomer including at least 50% by weight of said virgin thermoplastic material.
 16. The molded shoe outsole of claim 15 wherein said virgin thermoplastic material includes a virgin thermoplastic rubber.
 17. The molded shoe outsole of claim 16 wherein the remaining portion of said filled elastomer includes reground thermoplastic rubber.
 18. The molded shoe outsole of claim 17 wherein said filled elastomer includes about 30% by weight of said recycled rubber granules, about 50% by weight of said virgin thermoplastic rubber, and about 20% by weight of said reground thermoplastic rubber.
 19. A molded shoe outsole comprising: vulcanized rubber; and recycled rubber granules mixed with said vulcanized rubber in predetermined quantities to form a filled elastomer, said filled elastomer including at least 50% by weight of said vulcanized rubber and no more than about 30% by weight of said recycled rubber granules. 